Logging in two computers at the same time?

I have two computers each with their own touchscreen for authentication. When a user authenticates on one computer it also authenticates on the other computer and updates the screens asynchronously to the authenticated view. What is the best way to do this? The user story: As a user I need to login into a system using a single sign on on one computer but have all computers on the network become 'awake' when I log in.